For many years, the electronics industry has been aware of the threat posed by zinc whisker or zinc needle growth on zinc-electroplated surfaces. As technology has advanced, and processors, power sources, and the like have become increasingly smaller, a growing concern has developed with respect to these whisker-like conductive contaminants. This has been particularly a problem in the so-called “computer room” where zinc electroplated floor tiles are used to form grounds for computer components, as well as provide a convenient path for technicians to run cables and wires. On the bottom of some of these floor tiles, as well as in other locations, these whisker-like growths can form.
Generally, it is known that tin, zinc, and cadmium plating can grow whiskers. This type of plating is frequently used as corrosion protection for steel electronic enclosures. Some have proposed that certain electroplating processes impart internal stress in these metals, setting the stage for whisker growth. Though tin is more susceptible to whisker formation than either cadmium or zinc, zinc plating is more common in computer rooms and data center. This is because zinc plating is often applied to electronic enclosures, structural elements, and other equipment made of high strength, low alloy steel. Zinc whiskers are formed from metal surfaces coated with zinc in a galvanization process to help protect them from corrosion. The zinc whiskers generally can be described as zinc filaments extending from these treated surfaces. They are normally only a few microns in width, but can be several hundred to over a thousand microns in length.
The first zinc-plated enclosures in use with computer equipment presented some whisker problems, but these problems were easily remedied due to the large circuitry spacing and higher voltages used in the systems. However, as technology has become more sophisticated, zinc whiskers are creating a greater problem. For example, low voltages as are present in more modern systems are not capable of burning off metallic whiskers in a quick manner. It is also suspected that higher operating temperatures of systems as a whole encourage the incubation and growth of whisker-like particulates.
Zinc whisker growth has been found on sub-racks, switches, card cages, floor tiles, frames, internet routers, and other electroplated surfaces. They can also be found growing from certain computer hardware. However, if these whisker-like particulates become airborne, they can be found anywhere in a computer room or computer data center, or can be carried into a data center from an external source. Not all electroplated surfaces appear to exhibit whisker growth, and not all of such surfaces develop the problem at the same rate. Thus, it is suspected that whisker growth is affected to some extent by the environment in combination with the electroplated surface.
As previously stated, floor tiles are a location where zinc whisker growth is particularly prevalent. This is partly because these floor tiles have large surface areas, and are often disturbed during normal activity in a computer room or data center, e.g., removed by technicians or disturbed by running cable, etc. Additionally, raised floor tile construction used in most computer rooms is utilized as a duct for supplying necessary airflow to computer components. Because of this activity and airflow, zinc whiskers can easily be dislodged and carried to the hardware. Additionally, floor tiles are often dragged across the top of each other as they are removed from a floor grid, spreading tile contamination throughout the room.
A reason that zinc whiskers (or other undesired metallic particulates) cause failures or other problems in computer rooms is because they are conductive contaminants, and can actually cause shorts on circuit board cards, power supplies, or other electronic components. As computer circuitry has become smaller, and voltages have decreased generally, short metallic whiskers can span two electrically isolated features on a circuit board. Such a span can, for example, misdirect current causing unforeseen problems. Though the growth of zinc whiskers is not new, their ability to impact hardware reliability has been increased by denser geometries of the newer technologies.
Metallic particulates such as zinc whiskers have been discovered by visual inspection and/or by the wiping of an area with a swatch. Thus, in the prior art, the presence of zinc whiskers in data centers have been discovered using less precise methods than those of the present invention. Some of these prior art methods do not provide the detailed information sometimes necessary for determining the best approach for remediation. For example, with respect to wipe sampling, a wet wipe is used to sample an area. The wipe can then be sealed in a plastic bag and sent to an environmental lab where tests are conducted to determine whether zinc is present on the wipe. However, with this method, tile lab is not always able to determine if the zinc is in the form of a zinc whisker. Further, even if such a determination can be made, tile lab may not be able to accurately determine of the zinc whisker, the surface properties of the zinc whisker, or the concentration of zinc whiskers sampled from a given area.